import sys
sys.setrecursionlimit(10 ** 7)

class UnionFind():
	def __init__(self, size):
		self.table = [-1 for _ in range(size)]
		self.size = [1 for _ in range(size)]

	def find(self, x):
		if self.table[x] < 0:
			return x
		else:
			self.table[x] = self.find(self.table[x])
			return self.table[x]

	def unite(self, x, y):
		s1 = self.find(x)
		s2 = self.find(y)
		if s1 != s2:
			if self.table[s1] > self.table[s2]:
				self.table[s2] = s1
				self.table[s1] -= 1
				self.size[s1] += self.size[s2]
				self.size[s2] = 0
			else:
				self.table[s1] = s2
				self.table[s2] -= 1
				self.size[s2] += self.size[s1]
				self.size[s1] = 0

		return

l, r = map(int, input().split())
uf = UnionFind(r+1)
for i in range(l, r+1):
	for j in range(i*2, r+1, i):
		uf.unite(i, j)

ans = -1
for i in range(l, r+1):
	if uf.table[i] < 0:
		ans += 1
print(ans)